In recent years, there has been proposed a hybrid vehicle which is provided with an internal combustion engine and a rotary electric machine each functioning as a power source. One of the hybrid vehicles is known to have a power distribution mechanism through which the internal combustion engine and the rotary electric machine are connected with each other, so that the internal combustion engine can be operated to be changed between an operation state and a stopped state in response to a running state of the hybrid vehicle such as a vehicle speed and a depression amount of an acceleration pedal while the hybrid vehicle is running.
Among the hybrid vehicles as mentioned above, there are some hybrid vehicles which are different from a vehicle provided with only a conventional internal combustion engine functioning as a power source, and adapted to start an operation of the internal combustion engine by an output power of the rotary electric machine in place of starting the operation of the internal combustion engine by a cell motor.
Such a hybrid vehicle as mentioned above is known to have an operation starting apparatus for the internal combustion engine which can limit the output power of the rotary electric machine to reduce the consumption of electric power of the rotary electric machine (see for example Patent Document 1).
The previously mentioned operation starting apparatus is constructed to start the internal combustion engine by driving the rotary electric machine, connected with an output shaft of the internal combustion engine through a damper, with an aid of a battery. The operation starting apparatus comprises a rotational speed detection unit for detecting the rotational speed of the internal combustion engine, and a starting torque setting unit for gradually increasing the starting torque to be applied to the output shaft of the internal combustion engine at a low rotation time when the rotational speed of the internal combustion engine is lower than a predetermined value. The operation starting apparatus thus constructed can suppress the consumption of excessively large electric power generated in a drive starting operation of the rotary electric machine, thereby making it possible to reduce the electric power consumption for the starting operation of the internal combustion engine.